Eh, 14 hours/level = ~6 days /played from 70->80. A bit slower than the initial TBC 60->70 but to be honest not that bad.
I pushed pretty hard in TBC, a Rogue geared with full T2 + TF, and solo it took me around 4 days /played or so.
I just recently finished casually leveling a Warlock solo on a new server with some RL friends and it took 6 days /played total, wasn't that bad at all.


My biggest concern is that there are 8 instances from 60-70 but currently only 5 between 70-80. Maybe they will implement more, I'm not sure what's planned... but time is quickly running out if they aren't going to slip the release date.